Oxide catalyst for oxidation or ammoxidation

ABSTRACT

Disclosed is an oxide catalyst for use in catalytic oxidation or ammoxidation of propane or isobutane in the gaseous phase, which comprises a composition represented by the Mo 1 V a Sb b Nb c Z d O n  (wherein: Z is at least one element selected from the group consisting of tungsten, chromium, titanium, aluminum, tantalum, zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth, yttrium, gallium, rare earth elements and alkaline earth metals; and a, b, c, d, and n are, respectively, the atomic ratios of V, Sb, Nb, Z and O, relative to Mo), wherein 0.1≦a&lt;0.4, 0.1&lt;b≦0.4, 0.01≦c≦0.3, 0≦d≦1, with the proviso that a&lt;b, and n is a number determined by and consistent with the valence requirements of the other elements present. Also disclosed is a process for producing an unsaturated carboxylic acid or an unsaturated nitrile by using the above-mentioned oxide catalyst.

This application is a Divisional of U.S. application Ser. No. 11/483,655filed Jul. 11, 2006 now U.S. Pat. No. 7,378,541 which is a Divisional ofU.S. application Ser. No. 10/011,286 filed Dec. 11, 2001 now U.S. Pat.No. 7,109,144, which claims foreign priority to JAPAN 2000-378530 filedDec. 13, 2000, the entire contents of which are incorporated herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an oxide catalyst for use in catalyticoxidation or ammoxidation of propane or isobutene in the gaseous phase.More particularly, the present invention is concerned with an oxidecatalyst for use in catalytic oxidation or ammoxidation of propane orisobutene in the gaseous phase, which comprises, in a specific ratio,molybdenum (mo), vanadium (V), antimony (Sb), niobium (Nb), oxygen (O)and at least one element Z selected from the group consisting oftungsten, chromium, titanium, aluminum, tantalum, zirconium, hafnium,manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium,platinum, zinc, boron, indium, germanium, tin, lead, bismuth, yttrium,gallium, rare earth elements and alkaline earth metals, wherein theSb/Mo atomic ration (b) is larger than V/Mo atomic ratio (a), and theSb/Mo atomic ratio (b) does not exceed 0.4. By the use of the oxidecatalyst of the present invention in the oxidation or ammoxidation ofpropane or isobutene in the gaseous phase, (meth)acrylonitrile or(meth)acrylic acid can be produced with high selectivity and such highselectivity can be maintained for a long time, so that(meth)acrylonitrile or (meth)acrylic acid can be efficiently producedfor a long time.

The present invention is also concerned with a process for producing anunsaturated carboxylic acid or an unsaturated nitrile in the presence ofthe above-mentioned oxide catalyst.

2. Prior Art

Conventionally, there have been well known a process for producing(meth)acrylonitrile by ammoxidation of propylene or isobutylene, and aprocess for producing (meth)acrylic acid by oxidation of propylene orisobutylene. Recently, as substitutes for such processes for theammoxidation or oxidation of propylene or isobutylene, attention hasbeen attracted to a process for producing (meth)acrylonitrile or(meth)acrylic acid by a catalytic ammoxidation or oxidation in thegaseous phase, wherein propane or isobutane is used as a raw materialinstead of propylene or isobutylene. As catalysts for use in theseprocesses, a number of catalysts have been proposed.

Of the catalysts proposed, especially, an oxide catalyst comprisingMo—V—Sb—Nb has been attracting attention, since such an oxide catalysthas advantages in that the catalyst comprises elements having arelatively low volatility, the catalyst can be used for a catalyticammoxidation or oxidation in the gaseous phase at a low reactiontemperature, and (meth)acrylonitrile or (meth)acrylic acid can beproduced with relatively high selectivity and in relatively high yield.

Methods for producing (meth)acrylonitrile in the presence of the oxidecatalyst comprising Mo—V—Sb—Nb (hereinafter, frequently referred to asan “Mo—V—Sb—Nb oxide catalyst”) are disclosed in various patentdocuments, such as Unexamined Japanese Patent Application Laid-OpenSpecification Nos. 9-157241 (corresponding to U.S. Pat. No. 5,750,760and EP 0767164 A1), 10-28862, 10-81660, 10-310539, 10-330343, 11-42434,11-43314, 11-57479, 11-263745, 2000-1464, 2000-143244, WO 0012209 A1(corresponding to DE 1998325 T), and U.S. Pat. No. 6,043,185.

Methods for producing (meth)acrylic acid in the presence of theMo—V—Sb—Nb oxide catalyst are also disclosed in various patentdocuments, such as Unexamined Japanese Patent Application Laid-OpenSpecification Nos. 9-316023, 10-118491, 10-120617 (corresponding to U.S.Pat. Nos. 5,994,580 and 6,060,422), 10-137585, 11-285637, 11-343261,2000-51693, 11-343262, 10-36311, 10-45664, 9-278680 and 10-128112.

Each of the above-mentioned Mo—V—Sb—Nb oxide catalysts, which are usedfor producing (meth)acrylonitrile or (meth)acrylic acid, comprises anoxide represented by the following formula (a):MO₁V_(p)Sb_(q)Nb_(r)O_(m)  (a)

-   -   wherein p, q, r and m are, respectively, the atomic ratios of V,        Sb, Nb and O, relative to Mo.

The above-mentioned conventional Mo—V—Sb—Nb oxide catalysts can becategorized into the following two groups:

-   (i) catalysts in which the V/Mo atomic ratio is equal to or larger    than the Sb/Mo atomic ratio, i.e., p and q in formula (a) above    satisfy the following relationship: p≧q; and-   (ii) catalysts in which the Sb/Mo atomic ratio is larger than V/Mo    atomic ratio, i.e., p and q in formula (a) above satisfy the    following relationship: p<q,

wherein the Sb/Mo atomic ratio is equal to or larger than 0.5, i.e., qin formula (a) above satisfies the following relationship: q≧0.5.

When the conventional Mo—V—Sb—Nb oxide catalysts mentioned above areused, (meth)acrylonitrile or (meth)acrylic acid is sometimes producedwith a relatively high selectivity (hereinafter, (meth)acrylonitrile or(meth)acrylic acid is frequently referred to as the “desired product”).However, the selectivity for the desired product, which is achieved bysuch conventional catalysts, is not satisfactory.

Of the Mo—V—Sb—Nb oxide catalysts of group (i) above, oxide catalystscapable of achieving a relatively high selectivity for the desiredproduct exhibits a disadvantageously low stability. Specifically,especially when the catalytic oxidation or ammoxidation in the gaseousphase is performed in the presence of each of such oxide catalysts in arecycling mode using a gaseous feedstock mixture having a high partialpressure of propane, the selectivity for the desired product decreaseswith the lapse of time.

In an attempt to improve the stability of the Mo—V—Sb—Nb oxide catalystsof group (i) above so as to maintain the selectivity for the desiredproduct at a high level, the following two methods have been proposed:

-   -   a first method in which, using a reactor having a zone in which        a gaseous mixture having a higher oxygen concentration than that        of a gaseous reaction mixture produced is contacted with the        oxide catalyst, the oxide catalyst is continuously oxidized to        regenerate the oxide catalyst (see Unexamined Japanese Patent        Application Laid-Open Specification No. 11-263745); and    -   a second method in which an Mo—V—Sb—Nb oxide catalyst of        group (i) above produced by a process comprising preparing a raw        material liquid mixture for the catalyst, followed by        spray-drying and calcination is mixed with an aqueous solution        containing Mo and Co to obtain an aqueous mixture, and the        obtained aqueous mixture is spray-dried and calcined to thereby        obtain a modified catalyst containing a large amount of an Mo—Co        composite oxide (see Unexamined Japanese Patent Application        Laid-Open Specification No. 11-57479).

Of the above-mentioned two methods, the first method is disadvantageousin that the process for the catalytic ammoxidation or oxidation in thegaseous phase inevitably becomes cumbersome. On the other hand, thesecond method is also disadvantageous not only in that the process forproducing the oxide catalyst becomes too cumbersome, but also in that,even when silica is used to increase the strength of the catalyst, sincethe oxide catalyst produced in the second method contains a large amountof an Mo—Co composite oxide, it is difficult to cause the oxide catalystto contain a satisfactory amount of silica which is needed tosatisfactorily increase the strength of the oxide catalyst. Therefore,especially, it is difficult to apply the second method to the productionof an oxide catalyst which is used for a reaction in a fluidized bedand, hence, is required to have a high strength.

With respect to the Mo—V—Sb—Nb oxide catalysts of group (ii) above,these catalysts have a disadvantage in that the selectivity for thedesired product is low.

From the above, it is apparent that, by the conventional Mo—V—Sb—Nboxide catalysts for the catalytic ammoxidation or oxidation, it isdifficult to stably produce the desired compound with high selectivityfor a long time.

SUMMARY OF THE INVENTION

In this situation, the present inventors have made extensive andintensive studies toward developing an Mo—V—Sb—Nb oxide catalyst whichcan be used for stably producing (meth)acrylonitrile or (meth)acrylicacid with high selectivity for a long time. As a result, it hasunexpectedly been found that, by the use of a Mo—V—Sb—Nb oxide catalysthaving a specific composition in the oxidation or ammoxidation ofpropane or isobutane in the gaseous phase; (meth)acrylonitrile or(meth)acrylic acid can be produced with high selectivity and such highselectivity can be maintained for a long time. The above-mentionedMo—V—Sb—Nb oxide catalyst having a specific composition comprises, in aspecific ratio, molybdenum (Mo), vanadium (V), antimony (Sb), niobium(Nb), oxygen (O) and at least one element Z selected from the groupconsisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth,yttrium, gallium, rare earth elements and alkaline earth metals, whereinthe Sb/Mo atomic ratio (b) is larger than V/Mo atomic ratio (a), and theSb/Mo atomic ratio (b) does not exceed 0.4. Based on these novelfindings, the present invention has been completed.

Accordingly, it is a primary object of the present invention to providean Mo—V—Sb—Nb oxide catalyst which can be advantageously used for stablyproducing (meth)acrylonitrile or (meth)acrylic acid with highselectivity for a long time.

Another object of the present invention is to provide a process forproducing (meth)acrylonitrile, which comprises performing ammoxidationin the presence of the above-mentioned oxide catalyst, and a process forproducing (meth)acrylic acid, which comprises performing oxidation inthe presence of the above-mentioned oxide catalyst.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following detailed description andappended claims taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

In the drawings:

FIG. 1 is an X-ray diffraction pattern of the oxide catalyst obtained inExample 1; and

FIG. 2 is an enlarged view of the X-ray diffraction pattern of FIG. 1,showing the range of from 25 to 30° in terms of the diffraction angle(2θ), in order to explain how to obtain the peak intensity ratio.

DESCRIPTION OF REFERENCE NUMERALS

A₁: Apex of the peak observed at diffraction angle (2θ) of 27.1±0.3° inan X-ray diffraction pattern of the oxide catalyst obtained usingCuK_(α) as a source of X-ray;

A₂: Apex of the peak observed at diffraction angle (2θ) of 28.1±0.3° inan X-ray diffraction pattern of the oxide catalyst obtained usingCuK_(α) as a source of X-ray;

B₁: Point at which the curved line of the X-ray diffraction patternexhibits a minimum intensity value in the diffraction angle (2θ) rangeof 26.4±0.3°;

B₂: Point at which the curved line of the X-ray diffraction patternexhibits a minimum intensity value in the diffraction angle (2θ) rangeof 27.6±0.3°;

B₃: Point at which the curved line of the X-ray diffraction patternexhibits a minimum intensity value in the diffraction angle (2θ) rangeof 28.8±0.3°;

C₁: Point at which a straight line drawn downwardly from peak apex A₁vertically to the 2θ-axis intersects with a straight line connectingpoints B₁ and B₂; and

C₂: Point at which a straight line drawn downwardly from peak apex A₂vertically to the 2θ-axis intersects with a straight line connectingpoints B₂ and B₃

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, there is provided an oxide catalystfor use in catalytic oxidation or ammoxidation of propane or isobutanein the gaseous phase, which comprises a composition represented by thefollowing formula (I):Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I)

-   -   wherein:    -   Z is at least one element selected from the group consisting of        tungsten, chromium, titanium, aluminum, tantalum, zirconium,        hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,        palladium, platinum, zinc, boron, indium, germanium, tin, lead,        bismuth, yttrium, gallium, rare earth elements and alkaline        earth metals; and    -   a, b, c, d, and n are, respectively, the atomic ratios of        vanadium (V), antimony (Sb), niobium (Nb), Z and oxygen (O),        relative to molybdenum (Mo),        -   wherein:        -   0.1≦a<0.4,        -   0.1<b≦0.4,        -   0.01≦c≦0.3,        -   0≦d≦1,        -   with the proviso that a<b, and        -   n is a number determined by and consistent with the valence            requirements of the other elements present.

For easy understanding of the present invention, the essential featuresand various preferred embodiments of the present invention areenumerated below.

-   1. An oxide catalyst for use in catalytic oxidation or ammoxidation    of propane or isobutane in the gaseous phase, which comprises a    composition represented by the following formula (I):    Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I)    -   wherein:    -   Z is at least one element selected from the group consisting of        tungsten, chromium, titanium, aluminum, tantalum, zirconium,        hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,        palladium, platinum, zinc, boron, indium, germanium, tin, lead,        bismuth, yttrium, gallium, rare earth elements and alkaline        earth metals; and    -   a, b, c, d, and n are, respectively, the atomic ratios of        vanadium (V), antimony (Sb), niobium (Nb), Z and oxygen (O),        relative to molybdenum (Mo).        -   wherein:        -   0.1≦a<0.4,        -   0.1<b≦0.4,        -   0.01≦c≦0.3,        -   0≦d≦1,        -   with the proviso that a<b, and        -   n is a number determined by and consistent with the valence            requirements of the other elements present.-   2. The oxide catalyst according to item 1 above, wherein a in    formula (I) satisfies the following relationship: 0.1≦a≦0.3.-   3. The oxide catalyst according to item 1 above, wherein b in    formula (I) satisfies the following relationship: 0.1<b≦0.35.-   4. The oxide catalyst according to item 1 above, wherein c in    formula (I) satisfies the following relationship: 0.05≦c≦0.2.-   5. The oxide catalyst according to item 1 above, wherein a in    formula (I) satisfies the following relationship: 0.15≦a≦0.28.-   6. The oxide catalyst according to item 1 above, wherein b in    formula (I) satisfies the following relationship: 0.2≦b≦0.33.-   7. The oxide catalyst according to item 1 above, wherein c in    formula (I) satisfies the following relationship: 0.05≦c≦0.15.-   8. The oxide catalyst according to item 1 above, wherein a, b and c    in formula (I) satisfy the following relationships:

$\begin{matrix}{{0.15 \leq a \leq 0.28};} \\{{0.2 \leq b \leq 0.33};} \\{{0.05 \leq c \leq 0.15};} \\{{0.5 \leq {a + b + c} \leq 0.69};} \\{{\frac{a}{a + b + c} \geq 0.23};{and}} \\{{0.59 - \frac{0.528a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.7 - {\frac{0.524a}{a + b + c}.}}}\end{matrix}$

-   9. The oxide catalyst according to item 1 above, wherein a, b and c    in formula (I) satisfy the following relationships:

$\begin{matrix}{{0.16 \leq a \leq 0.28};} \\{{0.24 \leq b \leq 0.33};} \\{{0.07 \leq c \leq 0.15};} \\{{0.53 \leq {a + b + c} \leq 0.67};} \\{{\frac{a}{a + b + c} \geq 0.26};{and}} \\{{0.63 - \frac{0.549a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.68 - {\frac{0.529a}{a + b + c}.}}}\end{matrix}$

-   10. The oxide catalyst according to item 1 above, wherein a, b and c    in formula (I) satisfy the following relationships:

$\begin{matrix}{{0.16 \leq a \leq 0.26};} \\{{0.24 \leq b \leq 0.30};} \\{{0.08 \leq c \leq 0.12};} \\{{0.57 \leq {a + b + c} \leq 0.60};} \\{{\frac{a}{a + b + c} \geq 0.28};{and}} \\{{0.67 - \frac{0.5975a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.67 - {\frac{0.5352a}{a + b + c}.}}}\end{matrix}$

-   11. The oxide catalyst according to item 1 above, which exhibits, in    an X-ray diffraction pattern thereof obtained using CuK_(α) as a    source of X-ray, peaks at diffraction angles (2θ) of:

22.1±0.3°, 28.1±0.3°, 36.1±0.3° and 45.2±0.3°;

7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 35.2±0.3° and 45.2±0.3°; or

7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°,36.1±0.3° and 45.2±0.3°.

-   12. The oxide catalyst according to item 1 above, which further    comprises a silica carrier having supported thereon the oxide    catalyst, wherein the silica carrier is present in an amount of from    20 to 60% by weight in terms of SiO₂, based on the total weight of    the oxide catalyst and the silica carrier in terms of SiO₂.-   13. The oxide catalyst according to item 1 above, wherein Z in    formula (I) is at least one element selected from the group    consisting of tungsten, chromium, titanium, aluminum, tantalum,    zirconium, iron, boron, indium, germanium and tin.-   14. The oxide catalyst according to item 1 above, which is produced    by a method comprising providing an aqueous raw material mixture    containing compounds of molybdenum, vanadium, antimony, niobium and    optionally Z, and drying the aqueous raw material mixture, followed    by calcination.-   15. The oxide catalyst according to item 14 above, wherein the    calcination is performed at 500 to 700° C. in an atmosphere of inert    gas which is substantially free of molecular oxygen.-   16. The oxide catalyst according to item 14 above, wherein the    aqueous raw material mixture further contains oxalic acid, wherein    the molar ratio of the oxalic acid to the niobium compound in terms    of niobium is in the range of from 1 to 10.-   17. A process for producing acrylonitrile or methacrylonitrile,    which comprises reacting propane or isobutane with ammonia and    molecular oxygen in the gaseous phase in the presence of the oxide    catalyst of item 1 above.-   18. A process for producing acrylic acid or methacrylic acid, which    comprises reacting propane or isobutane with molecular oxygen in the    gaseous phase in the presence of the oxide catalyst of item 1 above.

Hereinbelow, the present invention is described in detail.

The oxide catalyst of the present invention is for use in catalyticoxidation or ammoxidation of propane or isobutane in the gaseous phase,and comprises a composition represented by the following formula (I):Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I).

In formula (I), Z is at least one element selected from the groupconsisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth,yttrium, gallium, rare earth elements and alkaline earth metals.

It is preferred that Z is at least one element selected from the groupconsisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, iron, boron, indium, germanium and tin. It is more preferredthat Z is at least one element selected from the group consisting oftungsten, titanium, aluminum, iron and boron.

In formula (I), a, b, c, d and n are, respectively, the atomic ratios ofvanadium (V), antimony (Sb), niobium (Nb), Z and oxygen (O), relative tomolybdenum (Mo). Atomic ratios a, b, c and d are determined by thecharging ratios of the below-described raw material compounds used forproducing the oxide catalyst of the present invention.

In formula (I), a satisfies the relationship: 0.1≦a<0.4, preferably0.1≦a≦0.3, more preferably 0.15≦a≦0.28. When a<0.1 or a≧0.4, theselectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

In formula (I), b satisfies the relationship: 0.1<b≦0.4, preferably0.1<b≦0.35, more preferably 0.2≦b≦0.33. When b≦0.1 or b>0.4, theselectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

In formula (I), c satisfies the relationship: 0.01≦c≦0.3, preferably0.05≦c≦0.2, more preferably 0.05≦c≦0.15. When c<0.01 or c>0.3, theselectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

In formula (I), d satisfies 0≦d≦1, preferably 0≦d≦0.4, more preferably0.01≦d≦0.1.

When Al is used as Z element, it is preferred that d satisfies therelationship: 0≦d≦0.1, more advantageously 0.01≦d≦0.05.

In formula (I), a and b satisfy the relationship: a<b. When a≧b, theselectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

In formula (I), n is a number determined by and consistent with thevalence requirements of the other elements present.

In an especially preferred embodiment of the present invention, a, b andc are within their respective more preferred ranges mentioned above.Specifically, in the especially preferred embodiment of the presentinvention, a, b and c in formula (I) satisfy the followingrelationships:

0.15≦a≦0.28:

0.2≦b≦0.33; and

0.05≦c≦0.15.

Further, in the especially preferred embodiment of the presentinvention, it is preferred that a, b and c not only are within theirrespective more preferred ranges mentioned above, but also satisfyspecific relationships. Specifically, it is preferred that a, b and c informula (I) satisfy the following relationships:

$\begin{matrix}{{0.15 \leq a \leq 0.28};} \\{{0.2 \leq b \leq 0.33};} \\{{0.05 \leq c \leq 0.15};} \\{{0.5 \leq {a + b + c} \leq 0.69};} \\{{\frac{a}{a + b + c} \geq 0.23};{and}} \\{{0.59 - \frac{0.528a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.7 - {\frac{0.524a}{a + b + c}.}}}\end{matrix}$

It is more preferred that a, b and c in formula (I) satisfy thefollowing relationships:

$\begin{matrix}{{0.16 \leq a \leq 0.28};} \\{{0.24 \leq b \leq 0.33};} \\{{0.07 \leq c \leq 0.15};} \\{{0.53 \leq {a + b + c} \leq 0.67};} \\{{\frac{a}{a + b + c} \geq 0.26};{and}} \\{{0.63 - \frac{0.549a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.68 - {\frac{0.529a}{a + b + c}.}}}\end{matrix}$

It is still more preferred that a, b and c in formula (I) satisfy thefollowing relationships:

$\begin{matrix}{{0.16 \leq a \leq 0.26};} \\{{0.24 \leq b \leq 0.30};} \\{{0.08 \leq c \leq 0.12};} \\{{0.57 \leq {a + b + c} \leq 0.60};} \\{{\frac{a}{a + b + c} \geq 0.28};{and}} \\{{0.67 - \frac{0.5975a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.67 - {\frac{0.5352a}{a + b + c}.}}}\end{matrix}$

It is preferred that the oxide catalyst of the present inventionexhibits, in an X-ray diffraction pattern thereof obtained using CuK_(α)as a source of X-ray, peaks at diffraction angles (2θ) of:

22.1±0.3°, 28.1±0.3°, 36.1±0.3° and 45.2±0.3°;

7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 35.2±0.3° and 45.2±0.3°; or

7.8±0.3, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3°and 45.2±0.3°.

It is especially preferred that the oxide catalyst of the presentinvention exhibits, in an X-ray diffraction pattern thereof obtainedusing CuK_(α) as a source of X-ray, peaks at diffraction angles (2θ) of7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°,36.1±0.3° and 45.2±0.3°.

In the present invention, the X-ray diffraction (XRD) analysis isconducted under the following conditions:

Tube voltage 40 kV Tube current 190 mA Divergence slit 1° Scatter slit1° Receiving slit 0.3 mm Scanning speed 5°/min. Sampling interval 0.02°

The oxide catalyst which exhibits, in an X-ray diffraction (XRD) patternthereof, peaks at the above-mentioned diffraction angles advantageouslyexhibits a high catalytic activity and a high selectivity for thedesired compound. The reason why such an oxide catalyst exhibits a highcatalytic activity and a high selectivity for the desired compound hasnot yet been elucidated. However, it is presumed that such an oxidecatalyst contains an oxide which exhibits, in an XRD pattern thereofobtained using CuK_(α) as a source of X-ray, peaks at diffraction angles(2θ) of 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and 45.2±0.3°; and/or an oxidewhich exhibits, in an XRD thereof obtained using CuK_(α) as a source ofX-ray, peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°,22.1±0.3°, 27.1±0.3°, 35.2±0.3° and 45.2±0.3°; and that such an oxide oroxides contribute to the improvement of the performance of the oxidecatalyst.

The oxide catalyst of the present invention may exhibit, in the XRDpattern thereof, in addition to the above-mentioned peaks, a peak havinga high intensity, as long as the performance of the oxide catalyst isnot harmfully affected.

Hereinafter, a peak appearing at a certain diffraction angle (2θ) ofx±0.3° is designated as “P^(X)” (for example, a peak appearing atdiffraction angle (2θ) of 7.8±0.3° is designated as P^(7.8)).

In the present invention, it is preferred that when the intensity ofP^(22.1) is taken as 100,

the intensity of P^(7.8) is from 0.5 to 30,

the intensity of P^(8.9) is from 0.5 to 3.0,

the intensity of P^(27.1) is from 3 to 90,

the intensity of P^(28.1) is from 10 to 300.

the intensity of P^(35.2) is from 0.5 to 30,

the intensity of P^(36.1) is from 5 to 50, and

the intensity of P^(45.2) is from 3 to 30.

The intensity of a peak appearing in an XRD pattern can be obtained asfollows. For example, a method for obtaining the intensities of P^(27.1)and P^(28.1) is explained below referring to FIG. 2, which is anenlarged view of the XRD pattern of FIG. 1 (XRD pattern of the oxidecatalyst obtained in Example 1), showing the range of from about 25° toabout 30° in terms of the diffraction angle (2θ).

In FIG. 2, characters A₁ and A₂ designate the apexes of P^(27.1) andP^(28.1), respectively.

Characters B₁, B₂ and B₃ respectively designate points at which thecurved line of the XRD pattern exhibits minimum intensity values in thediffraction angle (2θ) ranges of 26.4±0.3°, 27.6±0.3° and 28.8±0.3°,respectively (these diffraction angle (2θ) ranges are selected to obtainan appropriate base line (i.e., line connecting B₁, B₂ and B₃) forobtaining the intensities of the peaks). In the present invention,usually, each of “the points at which the curved line of the XRD patternexhibits minimum intensity values” corresponds to a point at which thegradient of a tangential line of the curved line shifts from negative topositive, or a point at which the gradient converges to zero, whereinthe gradient is taken in the coordinates of the 2θ-axis and theintensity axis.

Character C₁ designates a point at which a line drawn downwardly frompeak apex A₁ vertically to the 2θ-axis intersects with a straight lineconnecting points B₁ and B₂.

Character C₂ designates a point at which a line drawn downwardly frompeak apex A₂ vertically to the 2θ-axis intersects with a straight lineconnecting points B₂ and B₃.

The intensity of P^(27.1) is defined as the length of straight linesegment A₁C₁ which extends from peak apex A₁ (of P^(27.1)) to point C₁;and the intensity of P^(28.1) is defined as the length of straight linesegment A₂C₂ which extends from peak apex A₂ (of P^(28.1)) to point C₂.

The intensities of other peaks appearing in the XRD pattern can beobtained in substantially the same manner as mentioned above.Specifically, the intensities of other peaks can be obtained as follows.

The intensity of P^(7.8) is defined as the length of straight linesegment A^(7.8)C^(7.8) which extends from peak apex A^(7.8) (of P^(7.8))to point C^(7.8), wherein the point C^(7.8) is a point at which a linedrawn downwardly from peak apex A^(7.8) vertically to the 2θ-axisintersects with a straight line connecting points B^(7.1) and B^(9.1),wherein points B^(7.1) and B^(9.1) are points at which the curved lineof the X-ray diffraction pattern exhibits minimum intensity values inthe diffraction angle (2θ) ranges of 7.1±0.3° and 9.1±0.3°,respectively.

The intensity of P^(8.9) is defined as the length of straight linesegment A^(8.9)C^(8.9) which extends from peak apex A^(8.9) (of P^(8.9))to point C^(8.9), wherein the point C^(8.9) is a point at which a linedrawn downwardly from peak apex A^(8.9) vertically to the 2θ-axisintersects with a straight line connecting points B^(7.1) and B^(9.1),wherein points B^(7.1) and B^(9.1) are points at which the curved lineof the X-ray diffraction pattern exhibits minimum intensity values inthe diffraction angle (2θ) ranges of 7.1±0.3° and 9.1±0.3°,respectively.

The intensity of P^(22.1) is defined as the length of straight linesegment A^(22.1)C^(22.1) which extends from peak apex A^(22.1) (ofP^(22.1)) to point C^(22.1), wherein the point C^(22.1) is a point atwhich a line drawn downwardly from peak apex A^(22.1) vertically to the2θ-axis intersects with a straight line connecting points B^(21.1) andB^(22.9), wherein points B^(21.1) and B^(22.9) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 21.1±0.3° and 22.9±0.3°,respectively.

The intensity of P^(35.2) is defined as the length of straight linesegment A^(35.2)C^(35.2) which extends from peak apex A^(35.2) (ofP^(35.2)) to point C^(35.2), wherein the point C^(35.2) is a point atwhich a line drawn downwardly from peak apex A^(35.2) vertically to the2θ-axis intersects with a straight line connecting points B^(34.5) andB^(35.7), wherein points B^(34.5) and B^(35.7) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 34.5±0.3° and 35.7±0.3°,respectively.

The intensity of P^(36.1) is defined as the length of straight linesegment A^(36.1)C^(36.1) which extends from peak apex A^(36.1) (ofP^(36.1)) to point C^(36.1), wherein the point C^(36.1) is a point atwhich a line drawn downwardly from peak apex A^(36.1) vertically to the2θ-axis intersects with a straight line connecting points B^(35.7) andB^(36.5), wherein points B^(35.7) and B^(36.5) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 35.7±0.3° and 3.65±0.3°,respectively.

The intensity of P^(45.2) is defined as the length of straight linesegment A^(45.2)C^(45.2) which extends from peak apex A^(45.2) (ofP^(45.2)) to point C^(45.2), wherein the point C^(45.2) is a point atwhich a line drawn downwardly from peak apex A^(45.2) vertically to the2θ-axis intersects with a straight line connecting points B^(44.5) andB^(45.8), wherein points B^(44.5) and B^(45.8) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 44.5±0.3° and 45.8±0.3°,respectively.

In the present invention, it is preferred that the intensity ratio R isfrom 0.01 to 0.80, advantageously from 0.03 to 0.50, more advantageouslyfrom 0.05 to 0.20, wherein R is defined by the following formula:R=I ^(27.1)/(I ^(27.1) +I ^(28.1))wherein:

I^(27.1) represents the intensity of P^(27.1) (the peak appearing atdiffraction angle (2θ) of 27.1±0.3°), and

I^(28.1) represents the intensity of P^(27.1) (the peak appearing atdiffraction angle (2θ) of 28.1±0.3°).

It is preferred that the oxide catalyst of the present invention furthercomprises a silica carrier having supported thereon said oxide catalyst.That is, it is preferred that the oxide catalyst of the presentinvention is a silica-supported catalyst. In the pre-sent invention, itis preferred that the silica carrier is present in an amount of from 20to 60% by weight, more advantageously from 25 to 55% by weight, mostadvantageously from 40 to 50% by weight, based on the total weight ofthe oxide catalyst and the silica carrier.

The weight percentage of silica carrier is defined by the followingformula:weight percentage of silica carrier=(W2/(W1+W2))×100

-   -   wherein W1 represents the weight of oxide catalyst, which is        calculated from the composition of the raw materials and the        oxidation numbers of the component elements contained in the raw        materials, and W2 represents the weight of silica carrier, in        terms of SiO₂.

When the amount of silica carrier is less than 20% by weight,disadvantages are likely to occur wherein the strength of the oxidecatalyst becomes low, and the selectivity for and yield of(meth)acrylonitrile or (meth)acrylic acid, which are achieved by the useof the oxide catalyst, become low. On the other hand, when the amount ofsilica carrier is more than 60% by weight, the strength of the oxidecatalyst becomes high; however, the selectivity for and yield of(meth)acrylonitrile or (meth)acrylic acid, which are achieved by the useof the oxide catalyst, become low.

Next, an explanation is made below with respect to the compounds used inthe process for producing the oxide catalyst of the present invention assources of the component elements of the oxide catalyst, i.e., compoundsused as sources of molybdenum, vanadium, antimony, niobium, and theoptional component element Z.

Examples of sources of molybdenum include ammonium heptamolybdate,molybdenum oxides, molybdic acid, molybdenum oxychlorides, molybdenumchlorides, molybdenum alkoxides and the like. Of these, ammoniumheptamolybdate is preferred.

Examples of sources of vanadium include ammonium metavanadate, vanadium(V) oxide, vanadium oxychlorides, and vanadium alkoxides. Of these,ammonium metavanadate and vanadium (V) oxide are preferred.

Examples of sources of antimony include antimony(III) oxide,antimony(IV) oxide, antimony(V) oxide, metantimonic acids (III),antimonic acids (V), ammonium antimonate(V), antimony(III) chloride,antimony(III) oxychloride, antimony(III) nitrate oxide, antimonyalkoxides, organic acid salts of antimony, such as antimony tartrate,and metallic antimony. Of these, antimony(III) oxide is preferred.

Examples of sources of niobium include niobic acid, niobium oxide,niobium chloride, niobium alkoxides (such as Nb(OCH₂CH₃)₅) and organicsalts of niobium. Of these, niobic acid is preferred.

Examples of sources of Z elements include oxalic acid salts, hydroxides,oxides, nitrates, acetates, ammonium salts, carbonates and alkoxides ofthe Z elements.

The suitable amounts of the above-mentioned compounds as sources of thecomponent elements vary depending on the types of the compounds used,and the amounts are appropriately selected such that an oxide catalysthaving the composition represented by formula (I) is obtained.

When it is intended to use silica to obtain an oxide catalyst supportedon a silica carrier, silica sol can be advantageously used as a sourceof silica. It is especially preferred to use a silica sol stabilizedwith ammonium ions.

With respect to the process for producing the oxide catalyst of thepresent invention, there is no particular limitation. However, it ispreferred to produce the oxide catalyst of the present invention by aprocess comprising the following three steps: a step for providing anaqueous raw material mixture containing compounds of molybdenum,vanadium, antimony, niobium, and optionally component element Z (i.e.,step for preparing the aqueous raw material mixture), a step for dryingthe aqueous raw material mixture, and a step for calcining the resultantdried aqueous raw material mixture.

In the aqueous raw material mixture, the above-mentioned compounds usedas sources of molybdenum, vanadium, antimony, niobium and the optionalcomponent element Z may remain as they are, or may be present inmodified forms thereof which are formed by chemical reactions (e.g.,chemical reactions between the compounds used as raw materials).

Hereinbelow, explanations are made with respect to the step forproviding an aqueous raw material mixture (i.e., step for preparing theaqueous raw material mixture), the step for drying the aqueous rawmaterial mixture, and the step for calcining the resultant dried aqueousraw material mixture, wherein specific modes of the above-mentionedprocess for producing the oxide catalyst of the present invention aretaken as examples.

<Aqueous Raw Material Mixture Preparation Step>

An aqueous mixture containing ammonium heptamolybdate, ammoniummetavanadate and antimony(III) oxide is subjected to a reaction,preferably, at 70 to 100° C., while stirring for 1 to 5 hours. Theresultant mixture containing molybdenum, vanadium and antimony issubjected to an oxidation by air or an oxidation in a liquid phase byusing hydrogen peroxide or the like, to thereby obtain an aqueousmixture (A). It is preferred that the oxidation is conducted to anextent wherein the change in color of the aqueous mixture from dark blueto orange or brown is visually observed. In the case where the oxidationis conducted in a liquid phase by using hydrogen peroxide, the molarratio of hydrogen peroxide to antimony is preferably 0.5 to 2. Themolybdenum concentration of the aqueous mixture (A) is preferably 0.2mol/kg or more, more preferably 0.5 mol/kg or more.

Alternatively, to an aqueous solution having ammonium heptamolybdatedissolved therein are added antimony(III) oxide and aqueous hydrogenperoxide having a hydrogen peroxide concentration of 0.01 to 30% byweight (preferably 0.1 to 10% by weight), followed by stirring at 50 to80° C. The molar ratio of hydrogen peroxide to antimony is preferably0.5 to 5. To the resultant aqueous solution is added ammoniummetavanadate to obtain an aqueous mixture (A′). The molybdenumconcentration of the aqueous mixture (A′) is preferably 0.2 mol/kg ormore, more preferably 0.5 mol/kg or more.

On the other hand, a niobium-containing aqueous mixture (B) is preparedby dissolving a niobic acid in an aqueous oxalic acid solution. Theniobium concentration of the niobium-containing aqueous mixture (B) ispreferably 0.05 mol/kg or more, more preferably 0.15 mol/kg or more. Theoxalic acid/niobium molar ratio in the niobium-containing aqueousmixture (B) is preferably in the range of from 1 to 10, more preferablyfrom 2 to 6, most preferably from 2 to 4. For obtaining theabove-mentioned preferred oxide catalyst which exhibits, in the X-raydiffraction pattern, peaks at specific diffraction angles, it isespecially preferred that the oxalic acid/niobium molar ratio is in therange of from 2 to 4. However, when, prior to the below-describedcalcination step, pre-calcination is performed, the above-mentionedpreferred oxide catalyst can be obtained even if the oxalic acid/niobiummolar ratio is not in the range of from 2 to 4, but the molar ratio ispreferably in the range of from 1 to 10.

To the obtained niobium-containing aqueous mixture (B) may be addedaqueous hydrogen peroxide. The addition of aqueous, hydrogen peroxideenables the improvement of performance of the oxide catalyst, that is,it becomes possible to improve the space time yield and the selectivityfor the desired compound in a catalytic oxidation or ammoxidation ofpropane or isobutane in the gaseous phase. When aqueous hydrogenperoxide is added to the niobium-containing aqueous mixture (B), themolar ratio of hydrogen peroxide to niobic acid (in terms of niobiumatoms) is preferably in the range of from 0.5 to 10, more preferablyfrom 2 to 6.

By mixing the thus obtained aqueous mixture (A) or (A′) with the thusobtained niobium-containing aqueous mixture (B), the aqueous rawmaterial mixture can be obtained. The obtained aqueous raw materialmixture is subjected to the below-described drying step.

When it is intended to produce an oxide catalyst supported on a silicacarrier, a silica sol may be added at any time during the above-descriedprocedures to thereby obtain a silica sol-containing aqueous rawmaterial mixture, and the obtained silica sol-containing aqueous rawmaterial mixture is subjected to the below-described drying step.

When it is intended to produce an oxide catalyst containing the Zelement which is an optional component, a compound containing the Zelement may be added at any time during the above-descried procedures tothereby obtain a Z element-containing aqueous raw material mixture, andthe obtained Z element-containing aqueous raw material mixture issubjected to the below-described drying step.

<Drying Step>

The above-obtained aqueous raw material mixture is dried by spray dryingor evaporation drying to thereby obtain a dried powder. The spray dryingcan be conducted by centrifugation, by two-phase flow nozzle method orby high pressure nozzle method. As a heat source for drying, it ispreferred to use air which has been heated by steam, an electric heaterand the like. It is preferred that the temperature of the heated air atan entrance to the dryer section thereof is from 150 to 300° C. Thespray drying can be also conveniently conducted by spraying the aqueousraw material mixture onto an iron plate which has been heated to atemperature of 100 to 300° C.

For obtaining the above-mentioned preferred oxide catalyst whichexhibits, in the X-ray diffraction pattern, peaks at specificdiffraction angles, it is especially preferred to conduct the dryingstep by spray drying.

<Calcination Step>

In the calcination step, the dried powder obtained in the drying step iscalcined so as to obtain the oxide catalyst of the present invention.The calcination can be conducted by using a kiln, such as a rotary kiln,a tunnel kiln, a muffle kiln or a fluidized-bed kiln. The calcination isconducted in an atmosphere of an inert gas, such as nitrogen gas whichis substantially free of oxygen, or alternatively, in an atmospherecontaining an oxidative gas (such as an oxygen-containing gas) incombination with a reductive gas (such as a gaseous organic compound(e.g., propane or isobutane) or gaseous ammonia). The calcination ispreferably conducted in an atmosphere of an inert gas, such as nitrogengas which is substantially free of oxygen, more preferably under a flowof an inert gas, at a temperature of 500 to 700° C., preferably 570 to670° C. The time of calcination is generally 0.5 to 10 hours, preferably1 to 3 hours. It is preferred that the oxygen concentration of theabove-mentioned inert gas is 1000 ppm or less, more advantageously 100ppm or less, most advantageously 10 ppm or less, as measured by gaschromatography or by means of a trace oxygen analyzer. The calcinationcan be conducted repeatedly. Prior to the calcination, the dried powdermay be subjected to pre-calcination in an atmosphere of air or under astream of air at 200 to 420° C., preferably 250 to 350° C. for 10minutes to 5 hours. The catalyst obtained by calcination may besubjected to further calcination in an atmosphere of air at atemperature of from 200 to 400° C. for 5 minutes to 5 hours.

The thus produced oxide catalyst of the present invention can be used asa catalyst for producing (meth)acrylonitrile by ammoxidation of propaneor isobutane in the gaseous phase. The oxide catalyst of the presentinvention can also be used as a catalyst for producing (meth)acrylicacid by oxidation of propane or isobutane in the gaseous phase. Theoxide catalyst of the present invention is preferably used as a catalystfor producing (meth)acrylonitrile, more preferably as a catalyst forproducing acrylonitrile.

Propane or isobutane used for producing (meth)acrylic acid, and propaneor isobutane and ammonia used for producing (meth)acrylonitrile need notbe of very high purity but may be of a commercial grade.

Examples of sources of molecular oxygen fed into the reaction systeminclude air, oxygen-rich air, and pure oxygen. Further, such a source ofmolecular oxygen may be diluted with steam, helium, argon, carbondioxide, nitrogen or the like.

In the case of an ammoxidation reaction in the gaseous phase, the molarratio of ammonia to propane or isobutane for the ammoxidation isgenerally in the range of from 0.1 to 1.5, preferably from 0.2 to 1.2.When the ammoxidation is performed in a recycling mode, the molar ratioof ammonia to propane or isobutane at the entrance of a reactor used ispreferably in the range of from 0.2 to 1.0, more preferably from 0.5 to0.8.

The molar ratio of molecular oxygen to propane or isobutane used for theammoxidation is preferably in the range of from 0.2 to 6, morepreferably from 0.4 to 4. When the ammoxidation is performed in arecycling mode, it is preferred that the molar ratio of molecular oxygento propane or isobutane at the entrance of the reactor used ispreferably in the range of 0.8 to 2.2, more preferably from 1.5 to 1.9.

In the case of an oxidation reaction in the gaseous phase, the molarratio of molecular oxygen to propane or isobutane used for the oxidationis generally in the range of from 0.1 to 10, preferably from 0.1 to 5.It is preferred that steam is introduced into the reaction system. Themolar ratio of steam to propane or isobutane used for the oxidation isgenerally in the range of from 0.1 to 70, preferably from 3 to 40.

In each of the ammoxidation reaction in the gaseous phase and theoxidation reaction in the gaseous phase, the reaction pressure isgenerally in the range of from 0.01 to 1 MPa, preferably from 0.1 to 0.3MPa, in terms of the absolute pressure.

In the ammoxidation reaction in the gaseous phase, the reactiontemperature is generally in the range of from 300 to 600° C., preferablyfrom 380 to 470° C.

In the oxidation reaction in the gaseous phase, the reaction temperatureis generally in the range of from 300 to 600° C., preferably from 350 to440° C.

In each of the ammoxidation reaction in the gaseous phase and theoxidation reaction in the gaseous phase, the time of contact (contacttime) between gaseous feedstocks (containing propane or isobutane,molecular oxygen and the like) and the catalyst is generally in therange of from 0.1 to 30 (g·sec/ml), preferably from 0.5 to 10(g·sec/ml). In the present invention, the contact time is determinedaccording to the following formula:

${{Contact}\mspace{14mu}{time}\mspace{14mu}( {{g \cdot \sec}\text{/}{mI}} )} = {\frac{W}{F} \times 60 \times \frac{273}{273 + T} \times \frac{P + 0.101}{0.101}}$

-   -   wherein:    -   W represents the weight (g) of the oxide catalyst contained in        the reactor;    -   F represents the flow rate (ml/min) of the gaseous feed stocks;    -   T represents the reaction temperature (° C.); and    -   P represents the reaction pressure (MPa) (gauge pressure).

Each of the ammoxidation reaction in the gaseous phase and the oxidationreaction in the gaseous phase can be conducted in a conventionalreactor, such as a fixed bed reactor, a fluidized-bed reactor or amoving bed reactor, preferably in a fluidized-bed reactor. The reactionmode may be either a one pass mode or a recycling mode. Of these tworeaction modes, a recycling mode is preferred.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in more detail withreference to the following Examples and Comparative Examples, whichshould not be construed as limiting the scope of the present invention.

(1) Conversion of Propane, Selectivity for Acrylonitrile and Selectivityfor Acrylic Acid:

In the following Examples and Comparative Examples, the results of theoxidation or ammoxidation were evaluated in terms of the conversion (%)of propane, the selectivity (%) for acrylonitrile and the selectivity(%) for acrylic acid, which are, respectively, defined as follows:

$\begin{matrix}{{{Conversion}\mspace{14mu}(\%)\mspace{14mu}{of}\mspace{14mu}{propane}} = {\frac{{mole}\mspace{14mu}{of}\mspace{14mu}{propane}\mspace{14mu}{reacted}}{{mole}\mspace{14mu}{of}\mspace{14mu}{propane}\mspace{14mu}{fed}} \times 100}} \\{{{Selectivity}\mspace{14mu}(\%)\mspace{14mu}{for}\mspace{14mu}{acrylonitrile}} = {\frac{{mole}{\mspace{11mu}\;}{of}\mspace{14mu}{acrylonitrile}\mspace{14mu}{formed}}{{mole}\mspace{14mu}{of}\mspace{14mu}{propane}\mspace{14mu}{reacted}} \times 100}} \\{{{Selectivity}\mspace{14mu}(\%)\mspace{14mu}{for}\mspace{14mu}{acrylic}\mspace{14mu}{acid}} = {\frac{{mole}{\mspace{11mu}\;}{of}\mspace{14mu}{acrylic}\mspace{14mu}{acid}\mspace{14mu}{formed}}{{mole}\mspace{14mu}{of}\mspace{14mu}{propane}\mspace{14mu}{reacted}} \times 100}}\end{matrix}$(2) X-Ray Diffractometry of Oxide Catalyst:

An X-ray diffraction (XRD) pattern of the oxide catalyst was obtained bysubjecting the oxide catalyst to measurement by X-ray diffractometryusing an X-ray diffractometer MXP-18 (manufactured and sold by MACScience Co. Ltd., Japan). The method for preparing a sample and XRDpattern measurement conditions are as follows.

<Preparation of a Sample>

About 0.5 g of the catalyst was placed in an agate mortar and subjectedto grinding for 2 minutes by manually operating an agate pestle. Theresultant catalyst powder was subjected to sifting, to thereby obtain apowdery catalyst having a particle size of 53 μm or less. The obtainedpowdery catalyst was placed on a sample-holding table for an XRD patternmeasurement. The table had a rectangular recess in the surface thereof(which has the following dimensions: a length of 20 mm, a width of 16 mmand a depth of 0.2 mm), and the powdery catalyst in the recess waspressed using a stainless steel spatula having a flat shape so that thesurface of the powdery catalyst became flat.

<XRD Pattern Measurement Conditions>

An XRD pattern measurement was conducted under the following conditions.

Source of X-ray CuK_(α1) + CuK_(α2) Detector Scintillation counterSingle crystal Graphite used for a monochromator Tube voltage 40 kV Tubecurrent 190 mA Divergence slit 1° Scatter slit 1° Receiving slit 0.3 mmScanning speed 5°/min. Sampling interval 0.02° Scanning method 2θ/θmethod

The diffraction angle (2θ) correction was conducted by performing acalibration using X-ray diffractometry data obtained with respect to asilicon powder. Further, a smoothing treatment of the XRD pattern wasperformed.

With respect to the obtained XRD pattern, the intensity ratio R isdefined by the following formula:R=I ^(27.1)/(I ^(27.1) +I ^(28.1))wherein:

I^(27.1) represents the intensity of P^(27.1) (the peak appearing atdiffraction angle (2θ) of 27.1±0.3°), and

I^(28.1) represents the intensity of P^(28.1) (the peak appearing atdiffraction angle (2θ) 28.1±0.3°).

EXAMPLE 1 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (4.5% by weight) was prepared asfollows.

To 1,000 g of water were added 250 g of ammonium heptamolybdate[(NH₄)₆Mo₇O₂₄.4H₂O], 38.1 g of ammonium metavanadate (NH₄VO₃) and 53.6 gof antimony(III) oxide (Sb₂O₃), and the resultant mixture was subjectedto a reaction under reflux in an oil bath in the air at 100° C. for 2hours, followed by cooling to 50° C. Subsequently, to the resultantreaction mixture was added 829 g of a silica sol having an SiO₂ contentof 30% by weight, followed by stirring for 30 minute. Then, to theresultant mixture was further added 250 g of 5 wt % aqueous hydrogenperoxide, and the resultant mixture was stirred at 50° C. for 1 hour toeffect an oxidation treatment, to thereby obtain an aqueous mixture (A).By the oxidation treatment, the color of the mixture changed from darkblue to brown.

On the other hand, to 150 g of water were added 22.3 g of niobic acid(Nb₂O₅ content: 76% by weight) and 43.4 g of oxalic acid dihydrate(H₂C₂O₄.2H₂O), and the resultant mixture was heated at 60° C. whilestirring to dissolve the niobic acid and oxalic acid dihydrate in thewater, followed by cooling to 30° C., to thereby obtain an aqueousniobium-oxalic acid solution (B).

The thus obtained aqueous niobium-oxalic acid solution (B) was added tothe above-prepared aqueous mixture (A), and the resultant mixture wasstirred at 50° C. for 30 minutes in the air, to thereby obtain anaqueous raw material mixture.

The obtained aqueous raw material mixture was subjected to a spraydrying by means of a centrifugation type spray-drying apparatus underconditions wherein the entrance and exit temperatures of the dryer ofthe spray-drying apparatus were 230° C. and 120° C., respectively, tothereby obtain a dried powder comprised of spherical particles. 100 g ofthe obtained dried powder was charged into a quartz container andcalcined in a kiln at 640° C. for 2 hours under a flow of nitrogen gasat a flow rate of 600 Nml/min. (Nml means ml as measured under thenormal temperature and pressure conditions, namely, at 0° C. under 1atm.) while rotating the quartz container, to thereby obtain an oxidecatalyst. The oxygen concentration of the nitrogen gas used for thecalcination was determined by means of a trace oxygen analyzer (Model306WA, manufactured and sold by Teledyne Analytical Instruments,U.S.A.), and it was found that the oxygen concentration of the nitrogengas was 1 ppm.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

With respect to the obtained oxide catalyst, the X-ray diffraction (XRD)pattern obtained using CuK_(α) as a source of X-ray is shown in FIG. 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.08.

(Ammoxidation of Propane)

0.35 g of the obtained oxide catalyst (W=0.35 g) was charged into afixed-bed type reaction tube having an inner diameter of 4 mm. A gaseousfeedstock mixture having a molar ratio of propane:ammonia:oxygen:heliumof 1:0.7:1.7:5.3 was fed into the reaction tube at a flow rate (F) of3.6 (ml/min). The reaction temperature (T) (external temperature) was420° C. and the reaction pressure (P) was 0 MPa in terms of the gaugepressure. The contact time between the oxide catalyst and the gaseousmixture of the feedstocks was 2.3 (g·sec/ml). The contact time wasobtained by the following formula:

${{Contact}\mspace{14mu}{time}} = {\frac{W}{F} \times 60 \times \frac{273}{273 + T} \times \frac{P + 0.101}{0.101}}$

The produced gaseous reaction mixture was analyzed by means of anon-line gas chromatography apparatus. The results are shown in Table 1.

EXAMPLE 2 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of antimony(III) oxide(Sb₂O₃) was changed from 53.6 g to 51.6 g, the amount of 5 wt % aqueoushydrogen peroxide was changed from 250 g to 241 g and the amount ofsilica sol was changed from 829 g to 823 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 2.21±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.09.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in the same manner as in Example 1. The results are shownin Table 1.

EXAMPLE 3 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.24)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of ammonium metavanadate(NH₄VO₃) was changed from 38.1 g to 39.7 g, the amount of antimony(III)oxide (Sb₂O₃) was changed from 53.6 g to 51.6 g, the amount of 5 wt %aqueous hydrogen peroxide was changed from 250 g to 241 g and the amountof silica sol was changed from 829 g to 827 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3° wherein R=0.09.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in the same manner as in Example 1. The results are shownin Table 1.

EXAMPLE 4 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.24)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of ammonium metavanadate(NH₄VO₃) was changed from 38.1 g to 39.7 and the amount of silica solwas changed from 829 g to 833 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.10.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in the same manner as in Example 1. The results are shownin Table 1.

EXAMPLE 5 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.25)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of ammonium metavanadate(NH₄VO₃) was changed from 38.1 g to 41.4 g and the amount of silica solwas changed from 829 g to 836 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.10.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in the same manner as in Example 1. The results are shownin Table 1.

EXAMPLE 6 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.20)Sb_(0.29)Nb_(0.11)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate (NH₄VO₃) was changed from 38.1 g to 33.1 g, the amount ofantimony(III) oxide (Sb₂O₃) was changed from 53.6 g to 59.8 g, theamount of 5 wt % aqueous hydrogen peroxide was changed from 250 g to 279g and the amount of silica sol was changed from 829 g to 846 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 180 g, the amount of niobicacid was changed from 22.3 g to 27.2 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 53.0 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.14.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 3.3 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 2.5 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 7 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.22)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of ammonium metavanadate(NH₄VO₃) was changed from 38.1 g to 36.4 g and the amount of silica solwas changed from 829 g to 825 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.08.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in the same manner as in Example 1. The results are shownin Table 1.

EXAMPLE 8 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.22)Sb_(0.27)Nb_(0.10)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 36.4 g, the amount ofantimony(III) oxide was changed from 53.6 g to 55.7 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 260 g and theamount of silica sol was changed from 829 g to 836 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 165 g, the amount of niobicacid was changed from 22.3 g to 24.7 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 48.2 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.12.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 3.4 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 2.4 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 9 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.17)Sb_(0.30)Nb_(0.12)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 28.2 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 846 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 200 g, the amount of niobicacid was changed from 22.3 g to 29.7 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 57.8 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3° wherein R=0.16.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 3.2 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 2.6 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 10 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂ (40% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of antimony(III) oxide(Sb₂O₃) was changed from 53.6 g to 51.6 g, the amount of 5 wt % aqueoushydrogen peroxide was changed from 250 g to 241 g and the amount ofsilica sol was changed from 829 g to 671 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.30°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.10.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 4.0 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 2.1 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 11 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that 173 g of 5 wt % aqueous hydrogenperoxide was further added to aqueous niobium-oxalic acid solution (B).

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 1.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.08.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 4.7 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 1.7 (g·sec/ml). The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 47.5 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 221 g and theamount of silica sol was changed from 829 g to 826 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 116 g, the amount of niobicacid was changed from 22.3 g to 17.3 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 33.7 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.18.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1. Theresults are shown in Table 2.

COMPARATIVE EXAMPLE 2 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.15)Nb_(0.05)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 30.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 144 g and theamount of silica sol was changed from 829 g to 771 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 83 g, the amount of niobicacid was changed from 22.3 g to 12.4 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 24.1 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.10.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 3.7 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 2.2 (g·sec/ml). The results are shown in Table 2.

COMPARATIVE EXAMPLE 3 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.20)Nb_(0.05)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 41.3 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 192 g and theamount of silica sol was changed from 829 g to 800 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 83 g, the amount of niobicacid was changed from 22.3 g to 12.4 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 24.1 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.12.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1. Theresults are shown in Table 2.

COMPARATIVE EXAMPLE 4 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.25)Sb_(0.5)Nb_(0.125)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 41.4 g, the amount ofantimony(III) oxide was changed from 53.6 g to 103.2 g, the amount of 5wt t aqueous hydrogen peroxide was changed from 250 g to 481 g and theamount of silica sol was changed from 829 g to 989 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 210 g, the amount of niobicacid was changed from 22.3 g to 30.9 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 60.3 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and45.2±0.3°, but not at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°,27.1±0.3° and 35.2±0.3°.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 2.0 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 4.2 (g·sec/ml). The results are shown in Table 2.

COMPARATIVE EXAMPLE 5 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.3)Sb_(0.3)Nb_(0.1)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 881 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 166 g, the amount of niobicacid was changed from 22.3 g to 24.7 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 48.2 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.06.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1. Theresults are shown in Table 2.

COMPARATIVE EXAMPLE 6 Preparation of a Catalyst

An oxide catalyst represented by the formula:MO₁V_(0.3)Sb_(0.3)Nb_(0.05)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 855 g; and

in the preparation of aqueous niobium-oxalic acid solution (B), theamount of water was changed from 150 g to 84 g, the amount of niobicacid was changed from 22.3 g to 12.4 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 24.1 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.12.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 2.0 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 4.2 (g·sec/ml). The results are shown in Table 2.

COMPARATIVE EXAMPLE 7 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.3)Sb_(0.3)O_(n)/SiO₂ (45% by weight) was prepared as follows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that:

in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 830 g; and

aqueous niobium-oxalic acid solution (B) was not used.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 2.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 22.1±0.3°, 27.1±0.3°, 28.1±0.3°,35.2±0.3°, 36.1±0.3° and 45.2±0.3°, but not at diffraction angles (2θ)of 7.8±0.3° and 8.9±0.3°.

(Ammoxidation of Propane)

Using the obtained oxide catalyst, the ammoxidation reaction of propanewas performed in substantially the same manner as in Example 1, exceptthat flow rate (F) of the gaseous feedstock mixture was changed from 3.6(ml/min) to 2.0 (ml/min) and the contact time was changed from 2.3(g·sec/ml) to 4.2 (g sec/ml). The results are shown in Table 2.

TABLE 1 Conditions of the Ammoxidation of propane⁽*²⁾ catalystproduction Conversion Selectivity for process⁽*¹⁾ Contact of propaneacrylonitrile Composition H₂C₂O₄/Nb H₂O₂/Sb H₂O₂/Nb time (S) (%) (%) Ex.1 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.3 48.5 66.4Ex. 2 Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.3 48.466.4 Ex. 3 Mo₁V_(0.24)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.348.6 66.1 Ex. 4 Mo₁V_(0.24)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 02.3 48.2 66.2 Ex. 5 Mo₁V_(0.25)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.71 0 2.3 48.1 66.0 Ex. 6 Mo₁V_(0.20)Sb_(0.29)Nb_(0.11)O_(n)/SiO₂(45 wt %)2.7 1 0 2.5 48.9 64.8 Ex. 7 Mo₁V_(0.22)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45wt %) 2.7 1 0 2.3 48.7 65.8 Ex. 8Mo₁V_(0.22)Sb_(0.27)Nb_(0.10)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.4 48.7 65.5Ex. 9 Mo₁V_(0.17)Sb_(0.30)Nb_(0.12)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.6 48.264.8 Ex. 10 Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(40 wt %) 2.7 1 0 2.149.0 66.8 Ex. 11 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 12 1.7 49.5 68.0

TABLE 2 Conditions of the Ammoxidation of propane⁽*²⁾ catalystproduction Conversion Selectivity for process⁽*¹⁾ Contact of propaneacrylonitrile Composition H₂C₂O₄/Nb H₂O₂/Sb H₂O₂/Nb time (S) (%) (%)Com. Ex. 1 Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.348.3 63.3 Com. Ex. 2 Mo₁V_(0.30)Sb_(0.15)Nb_(0.05)O_(n)/SiO₂(45 wt %)2.7 1 0 2.2 48.8 61.3 Com. Ex. 3Mo₁V_(0.30)Sb_(0.20)Nb_(0.05)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.3 48.6 62.8Com. Ex. 4 Mo₁V_(0.25)Sb_(0.5)Nb_(0.125)O_(n)/SiO₂(45 wt %) 2.7 1 0 4.29.0 23.0 Com. Ex. 5 Mo₁V_(0.3)Sb_(0.3)Nb_(0.1)O_(n)/SiO₂(45 wt %) 2.7 10 2.3 40.0 53.0 Com. Ex. 6 Mo₁V_(0.3)Sb_(0.3)Nb_(0.05)O_(n)/SiO₂(45 wt%) 2.7 1 0 4.2 34.0 49.1 Com. Ex. 7 Mo₁V_(0.3)Sb_(0.3)O_(n)/SiO₂(45 wt%) 2.7 1 0 4.2 4.5 5.2 Notes for Tables 1 and 2: ⁽*¹⁾H₂C₂O₄/Nb: Oxalicacid/niobium molar ratio with respect to aqueous niobium-oxalic acidsolution (B) H₂O₂/Sb: Hydrogen peroxide/antimony molar ratio withrespect to the oxidation treatment of aqueous mixture (A) H₂O₂/Nb:Hydrogen peroxide/niobium molar ratio with respect to aqueousniobium-oxalic acid solution (B) ⁽*²⁾The reaction conditions for thecatalytic ammoxidation of propane in the gaseous phase are as follows.Composition of the gaseous feedstock mixture: [propane:ammonia:molecularoxygen:helium] molar ratio = 1:0.7:1.7:5.3 Reaction temperature: 420° C.

EXAMPLE 12 Ammoxidation of Propane

30 g of the oxide catalyst obtained in Example 1 was charged into aVycor glass fluidized-bed reaction tube having an inner diameter of 25mm. A gaseous feedstock mixture having a molar ratio ofpropane:ammonia:molecular oxygen:helium of 1:0.70:1.68:5.32 was fed intothe reaction tube at a flow rate of 420 (ml/min). The reactiontemperature was 440° C. (internal temperature), the reaction pressurewas 0.049 MPa in terms of the gauge pressure, and the contact time was2.4 (g·sec/ml).

24 Hours, 240 hours, 400 hours and 1000 hours after the start of thereaction, the produced gaseous reaction mixture was analyzed by means ofan on-line gas chromatography apparatus. The results are shown in Table3.

EXAMPLE 13

The ammoxidation reaction of propane was performed in substantially thesame manner as in Example 12, except that 30 g of the oxide catalystobtained in Example 1 was changed to 25 g of the oxide catalyst obtainedin Example 11, the flow rate (F) of the gaseous feedstock mixture waschanged from 420 (ml/min) to 460 (ml/min) and the contact time waschanged from 2.4 (g·sec/ml) to 1.8 (g·sec/ml). The results are shown inTable 3.

As apparent from the results of Examples 12 and 13, by the use of theoxide catalyst of the present invention, even in the continuouscatalytic ammoxidation of propane in the gaseous phase using a gaseousfeedstock mixture having a high partial pressure of propane, theselectivity for the desired product (i.e., acrylonitrile) is maintainedat a high level for a long time.

COMPARATIVE EXAMPLE 8

The ammoxidation reaction of propane was performed in substantially thesame manner as in Example 12, except that 30 g of the oxide catalystobtained in Example 1 was changed to 30 g of the oxide catalyst obtainedin the Comparative Example 1 (which exhibits, in the ammoxidationreaction of propane, the highest selectivity for acrylonitrile among theoxide catalysts obtained in Comparative Examples)) and the contact timewas changed from 2.4 (g·sec/ml) to 2.8 (g·sec/ml).

Since the oxide catalyst used was found to be deteriorated with thelapse of time, the flow rate (F) of the gaseous feedstock mixture wasappropriately controlled such that the conversion of propane wasmaintained at approximately 50%. 240 Hours after the start of thereaction, the flow rate was 380 (ml/min). 400 Hours after the start ofthe reaction, the flow rate was 360 (ml/min).

However, since the selectivity for acrylonitrile was markedly lowered,the reaction was terminated 400 hours after the start of the reaction.The results are shown in Table 3.

TABLE 3 Ammoxidation of propane⁽*¹⁾ 24 hours after the 240 hours afterthe 400 hours after the 1000 hours after the start of the reaction startof the reaction start of the reaction start of the reaction SelectivitySelectivity Selectivity Selectivity Conversion for Conversion forConversion for Conversion for of propane acrylonitrile of propaneacrylonitrile of propane acrylonitrile of propane acrylonitrileComposition (%) (%) (%) (%) (%) (%) (%) (%) Ex. 12Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/ 50.2 60.1 50.0 59.6 50.0 59.7 49.959.7 SiO₂(45 wt %) EX. 13 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/ 50.1 61.850.2 61.4 50.0 61.4 49.8 61.4 SiO₂(45 wt %) Comp.Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/ 50.0 57.6 50.0 54.5 50.0 52.7 Ex. 8SiO₂(45 wt %) Notes: ⁽*¹⁾The reaction conditions for the catalyticammoxidation of propane in the gasoous phase are as follows. Compositionof the gaseous feedstock mixture: [propane:ammonia:molecularoxygen:helium] molar ratio = 1:0.7:1.68:5.32 Reaction temperature: 440°C.

EXAMPLE 14 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (41% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Example 1, except that the amount of the silica sol waschanged from 829 g to 704 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 4.

The obtained oxide catalyst exhibits, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.08.

(Oxidation of Propane)

0.35 g of the obtained oxide catalyst (W=0.35 g) was charged into afixed-bed type reaction tube having an inner diameter of 4 mm. A gaseousfeedstock mixture having a molar ratio of propane:molecularoxygen:steam:helium of 1:3:14:10 was fed into the reaction tube at aflow rate (F) of 4.5 (ml/min). The reaction temperature (T) was 380° C.(external temperature) and the reaction pressure (P) was 0 MPa in termsof the gauge pressure. The contact time was 2.0 (g·sec/ml).

The produced gaseous reaction mixture was analyzed by means of a gaschromatography apparatus. The results are shown in Table 4.

COMPARATIVE EXAMPLE 9 Preparation of a Catalyst

An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂ (41% by weight) was prepared asfollows.

Preparation of an oxide catalyst was performed in substantially the samemanner as in Comparative Example 1, except that the amount of the silicasol was changed from 829 g to 702 g.

The composition of the oxide catalyst and the important conditions inthe catalyst production process are shown in Table 4.

The obtained oxide catalyst exhibited, in an XRD pattern thereof, peaksat diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°,28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, wherein R=0.18.

(Oxidation of Propane)

Using the obtained oxide catalyst, the oxidation of propane wasperformed in substantially the same manner as in Example 14. The resultsare shown in Table 4.

TABLE 4 Conditions of the Oxidation of propane⁽*2⁾ catalyst productionConversion Selectivity for process⁽*¹⁾ Contact of propane acrylic acidComposition H₂C₂O₄/Nb H₂O₂/Sb H₂O₂/Nb time (S) (%) (%) Ex. 14Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(41 wt %) 2.1 1 0 2.0 63.8 51.5Com. Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂(41 wt %) 2.7 1 0 2.0 63.548.1 Ex. 9 Notes: ⁽*¹⁾H₂C₂O₄/Nb: Oxalic acid/niobium molar ratio withrespect to aqueous niobium-oxalic acid solution (B) H₂O₂/Sb: Hydrogenperoxide/antimony molar ratio with respect to the oxidation treatment ofaqueous mixture (A) H₂O₂/Nb: Hydrogen peroxide/niobium molar ratio withrespect to aqueous niobium-oxalic acid solution (B) ⁽*2⁾The reactionconditions Eor the catalytic oxidation of propane in the gaseous phaseare as follows. Composition of the gaseous feedstock mixture:[propane:molecular oxygen:steam:helium) molar ratio = 1:3:14:10 Reactiontemperature: 380° C.

INDUSTRIAL APPLICABILITY

By the use of the oxide catalyst of the present invention in theoxidation or ammoxidation of propane or isobutane in the gaseous phase,(meth)acrylonitrile or (meth)acrylic acid can be produced with highselectivity and such high selectivity can be maintained for a long time,so that (meth)acrylonitrile or (meth)acrylic acid can be efficientlyproduced for a long time.

1. A process for producing acrylic acid or methacrylic acid, whichcomprises reacting propane or isobutane with molecular oxygen in thegaseous phase in the presence of an oxide catalyst, said oxide catalystcomprising a composition represented by the following formula (I):Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I) wherein: Z is at least one elementselected from the group consisting of tungsten, chromium, titanium,aluminum, tantalum, zirconium, hafnium, manganese, iron, ruthenium,cobalt, rhodium, nickel, palladium, platinum, zinc, boron, indium,germanium, tin, lead, bismuth, yttrium, gallium, rare earth elements andalkaline earth metals; and a, b, c, d, and n are, respectively, theatomic ratios of vanadium (V), antimony (Sb), niobium (Nb), Z and oxygen(O), relative to molybdenum (Mo), wherein: 0.1≦a<0.4, 0.1<b≦0.4,0.01≦c≦0.3, 0≦d≦1, with the proviso that a<b, and n is a numberdetermined by and consistent with the valence requirements of the otherelements present.
 2. The process according to claim 1, wherein a informula (I) satisfies the following relationship: 0.1≦a≦0.3.
 3. Theprocess according to claim 1, wherein b in formula (I) satisfies thefollowing relationship: 0.1<b≦0.35.
 4. The process according to claim 1,wherein c in formula (I) satisfies the following relationship:0.05≦c≦0.2.
 5. The process according to claim 1, wherein a in formula(I) satisfies the following relationship: 0.15≦a≦0.28.
 6. The processaccording to claim 1, wherein b in formula (I) satisfies the followingrelationship: 0.2≦b≦0.33.
 7. The process according to claim 1, wherein cin formula (I) satisfies the following relationship: 0.05≦c≦0.15.
 8. Theprocess according to claim 1, wherein a, b and c in formula (I) satisfythe following relationships: $\begin{matrix}{{0.15 \leq a \leq 0.28};} \\{{0.2 \leq b \leq 0.33};} \\{{0.05 \leq c \leq 0.15};} \\{{0.5 \leq {a + b + c} \leq 0.69};} \\{{\frac{a}{a + b + c} \geq 0.23};{and}} \\{{0.59 - \frac{0.528a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.7 - {\frac{0.524a}{a + b + c}.}}}\end{matrix}$
 9. The process according to claim 1, wherein a, b and c informula (I) satisfy the following relationships: $\begin{matrix}{{0.16 \leq a \leq 0.28};} \\{{0.24 \leq b \leq 0.33};} \\{{0.07 \leq c \leq 0.15};} \\{{0.53 \leq {a + b + c} \leq 0.67};} \\{{\frac{a}{a + b + c} \geq 0.26};{and}} \\{{0.63 - \frac{0.549a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.68 - {\frac{0.529a}{a + b + c}.}}}\end{matrix}$
 10. The process according to claim 1, wherein a, b and cin formula (I) satisfy the following relationships: $\begin{matrix}{{0.16 \leq a \leq 0.26};} \\{{0.24 \leq b \leq 0.30};} \\{{0.08 \leq c \leq 0.12};} \\{{0.57 \leq {a + b + c} \leq 0.60};} \\{{\frac{a}{a + b + c} \geq 0.28};{and}} \\{{0.67 - \frac{0.5975a}{a + b + c}} \leq \frac{b}{a + b + c}} \\{\leq {0.67 - {\frac{0.5352a}{a + b + c}.}}}\end{matrix}$
 11. The process according to claim 1, wherein said oxidecatalyst exhibits, in an X-ray diffraction pattern thereof obtainedusing CuK_(α) as a source of X-ray, peaks at diffraction angles (2θ) of:22.1±0.3°, 28.1±0.3°, 36.1±0.3° and 45.2±0.3°; 7.8±0.3°, 8.9±0.3°,22.1±0.3°, 27.1±0.3°, 35.2±0.3° and 45.2±0.3°; or 7.8±0.3°, 8.9±0.3°,22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°. 12.The process according to claim 1, wherein said oxide catalyst furthercomprises a silica carrier having supported thereon said oxide catalyst,wherein said silica carrier is present in an amount of from 20 to 60% byweight in terms of SiO₂, based on the total weight of said oxidecatalyst and said silica carrier in terms of SiO₂.
 13. The processaccording to claim 1, wherein Z in formula (I) is at least one elementselected from the group consisting of tungsten, chromium, titanium,aluminum, tantalum, zirconium, iron, boron, indium, germanium and tin.14. The process according to claim 1, wherein said oxide catalyst isproduced by a method comprising providing an aqueous raw materialmixture containing compounds of molybdenum, vanadium, antimony, niobiumand optionally Z, and drying said aqueous raw material mixture, followedby calcination.
 15. The process according to claim 14, wherein thecalcination is performed at 500 to 700° C. in an atmosphere of inert gaswhich is substantially free of molecular oxygen.
 16. The processaccording to claim 14, wherein said aqueous raw material mixture furthercontains oxalic acid, wherein the molar ratio of said oxalic acid tosaid niobium compound in terms of niobium is in the range of from 1 to10.
 17. The process according to claim 1, wherein d in formula (I)satisfies the following relationship: 0≦d≦0.4.